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Abstract In this paper, the flow softening and ductile damage of TC6 alloy were investigated using a uniaxial hot tensile test with deformation temperatures of 910 °C∼970 °C and strain rates of 0.01 s−1∼10 s−1. Scanning electron microscopy (SEM) was performed on the deformed specimens to reveal the damage mechanism. The results showed that the flow stress rapidly increases to a peak at a tiny strain, followed by a significant decrease due to flow softening and ductile damage. The ductile damage of the studied TC6 alloy can be ascribe to the nucleation, growth and coalescence of microdefects, and the microvoids preferentially nucleate at the interface of the alpha phase and beta matrix due to the inconsistent strain. Then, a set of unified viscoplastic constitutive equations including flow softening and ductile damage mechanisms was developed and determined, and this set of equations was verified by the experimental flow stress, which indicated the reliability of the prediction. Furthermore, the predicted normalized dislocation density and the adiabatic temperature rise increase with decreasing temperature and increasing strain rate. The predicted damage components show that the microdefects mainly nucleate in the initial stage, but then primarily grow and link together with continuing deformation. Highlights • The flow behaviour and ductile damage mechanism of TC6 alloy were investigated. • A set of physically-based internal-state-variable damage model was developed. • Normalized dislocation density and adiabatic temperature rise were predicted. • The microdefects mainly nucleate in the initial stage. • The microdefects primarily grow and link together with continuing deformation. [ABSTRACT FROM AUTHOR]

In this paper, the flow behaviour and globularization kinetics of a TC6 alloy were investigated by conducting hot compression tests at different temperatures (910–970 °C), strain rates (0.01–10.0 s-1) and true strains (0.223, 0.511, 0.916). Scanning electron microscopy (SEM) measurements were performed to evaluate the phase transformation and globularization fraction. Based on the experimental results, a set of internal state variable-based unified viscoplastic constitutive equations was developed to model the flow behaviour and the globularization evolution of the TC6 alloy. The model was fully determined by an optimization method based on genetic algorithm (GA). The results show that the predicted beta phase transformation curve fits the experimental data well, and that the predicted flow stress and globularization fraction of the alpha phase are in good agreement with the experimental data, even at strain rates outside the limits of the model. Furthermore, the flow stress begins to decrease at the onset of the softening mechanism, which occurs at a true strain of approximately 0.05. While an analysis of the predicted variations in the strain hardening rate and strain rate of each phase reveals that the softer beta phase accumulates more overall strain, whereas the strain accumulation in the alpha phase decrease. [ABSTRACT FROM AUTHOR]